Many sunken vessels throughout the world contain unknown amounts of oil, fuel, or other noxious liquids that pose a hazard to navigation and to the environment. Some of the sunken vessels are leaking these fluids, and others have the potential to start leaking at any time. A salvage operator needs to have the capability to determine how much liquid or gas is in a particular sunken vessel and thus to be able to make informed decisions as to its disposition. If the sunken ship must be pumped out, it is important that salvage divers know the location of any liquid/gas interface. By knowing the liquid/gas interface location, divers can avoid the dangers associated with tapping into a potentially explosive gas.
Various methods of detecting liquid/gas interfaces through a ship's hull have been investigated. These methods, which have met with limited success, have included using fish finders (echo sounders) that rely on a sonic pulse-echo to penetrate the hull of a sunken vessel and reveal the nature of its contents. Unless the hull and tanks are geometrically simple in shape and construction, the data from these types of echo sounders are difficult to interpret and are not reliable.
U.S. Pat. No. 4,403,508 to Langlois relates to a soundwave method and device for locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic impedance measurements. A high energy ultrasonic pulse is used. U.S. Pat. No. 4,203,324 to Baumoel discloses a sonic liquid level detector. Sonic pulses are reflected between the sides of a vessel containing the liquid. U.S. Pat. No. 4,144,517 to Baumoel reveals a single transducer liquid level detector. Decay rate of reflected sonic signals is an indication of the material on the other side of the plate. U.S. Pat. No. 3,019,650 to Worswick shows an apparatus for detecting the presence or absence of a body of liquid at a location. A transducer is coupled to the wall of the vessel. U.S. Pat. No. 2,990,543 to Rod discloses an earlier patent relating to the sensing of the presence or absence of material using "sonic" and ultrasonic transmission. These prior art systems are not satisfactory as liquid/gas level detectors because of difficulty in interpreting the output signals in ships and in use as self-contained units for undersea diver operation.
It is an object of this invention to increase the reliability and ease of making liquid/gas interface determinations in sunken vessels.
It is an object of the invention to provide a self-contained liquid/gas interface detector system capable of undersea operation.
It is a further object of the invention to provide a liquid/gas interface detector the sensitivity of which is not affected by thick steel plates (ship hull), marine growth, or transducer misalignment.